Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study

ABSTRACT Introduction: Class II division 1 malocclusion treatment with functional devices offers acceptable results. These devices can be removable or fixed, and the essential difference between them is the need for compliance. It is clinically important to investigate if there are differences in the treatment effects of these devices that present different characteristics. Objective: This retrospective longitudinal study compared the treatment effects of Class II correction with the MARA appliance, Activator-Headgear (AcHg) combination, both followed by multibracket fixed appliances, and an untreated control group. Material and Methods: Each experimental group was composed of 18 patients, with a baseline mean age of 11.70 and 10.88 years, treated for 3.60 and 3.17 years. The control group consisted of 20 subjects with baseline mean age of 11.07 years. The groups were evaluated before (T1) and after (T2) treatment. Lateral radiographs were used to evaluate the treatment changes with treatment (T2-T1), compared to the control group. Intergroup comparisons were performed using repeated-measures analysis of variance (ANOVA), followed by Tukey’s test. Results: The AcHg group showed significantly greater maxillary growth restriction than the MARA, while the mandibular changes were due to natural growth. Both devices promoted significantly greater maxillary incisors retrusion, mandibular incisors labial inclination, and improvement of overjet and molar relationships, compared to the control. Conclusions: Both functional devices followed by multibracket appliances were effective to correct Class II malocclusion. Nonetheless, the AcHg combination presents superior skeletal effects, due to significantly greater maxillary growth restriction compared to the MARA appliance. Moreover, the appliances presented similar dentoalveolar effects.


INTRODUCTION
Class II is considered one of the most frequent malocclusions in the orthodontic clinic. 1 Associated with this notable prevalence, there is an increased influx of patients searching for orthodontic treatment to treat this condition, due to its important aesthetic effect. 2 The orthodontist can choose from a great variety of therapeutic protocols to correct Class II cases, such as: the headgear, removable or fixed functional appliances, Class II intermaxillary elastics, or orthognathic surgery. 3 Since the main skeletal characteristic in Class II malocclusion is mandibular retrusion, and considering that protrusion of the maxilla is not often present, an approach able to redirect and stimulate mandibular growth with or without the restriction of maxillary growth would be strongly recommended. 4 In growing patients, an early intervention with a combination of functional and multibracket fixed appliances can yield optimal treatment outcomes for Class II malocclusion. 5 The activator and other removable functional appliances can modify Class II relationship by the transmission of soft-tissue tension to the dentition. This growth redirection can be obtained by positioning the mandible anteriorly with the appliance. 6 However, the use of removable devices, which depend heavily on patient compliance, is a recurrent concern of orthodontists during treatment. 6,7 Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 5 Among the fixed functional appliances, there is the Mandibular Anterior Repositioning Appliance (MARA). In MARA therapy the patient is led to position his/her mandible anteriorly at rest and during masticatory function, with the advantage of being a fixed device; therefore, requiring minimum patient compliance. 1,8 Thus, to treat Class II basal bones discrepancies the appliances should ideally generate skeletal and dental effects depending on minimal patient compliance.
Logically, the major difference between removable and fixed functional appliances is the needed amount of patient compliance. Few studies compared these different modalities and stated that removable functional appliances may be preferred when greater skeletal effects are desired. 9,10 On the other hand, evidence suggests that the effects of removable and fixed functional appliances are similar. 11 A recent systematic review concluded that there is still little evidence concerning the comparison of removable and fixed functional appliances. 12 Thus, there is a need for further studies to improve clinical decision-making about this subject. Because of this controversial scenario, this study aimed to investigate the treatment effects in Class II division 1 malocclusion patients treated either with the MARA or the Activator-Headgear (AcHg) combination, both followed Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 6 by multibracket fixed appliances. These groups were compared with an untreated control group of subjects with similar malocclusion.

MATERIAL AND METHODS
This retrospective longitudinal study was previously approved by the Ethics in Research Committee of Bauru Dentistry School, University of São Paulo (São Paulo/SP, Brazil).
Sample size calculation was based on an alpha error of 5% and a beta error of 20%. The minimum mean difference of 1.5 mm in the overjet, with a standard deviation of 1.57 mm was used, based on a previous study. 13 The sample size calculation showed that a minimum of 18 patients were required in each group.
The sample was selected from the orthodontic files of the an ANB angle greater than 4 degrees and overbite greater than Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 7 5 mm were present. The dentition developmental stage was not considered during patient records selection.
Exclusion criteria were applied to patients that were treated with different appliances, even when initially treated with the ones of the study; and in cases of patients with incomplete records or damaged dental casts.
Data recruitment and collection were performed by the same operators through August and September 2016. Data collected included: the clinical charts, to obtain the patients' age, general characteristics, and detailed information regarding treatment; dental casts (Class II malocclusion severity evaluation); and cephalometric radiographs at pre-(T1) and post-treatment after the use of orthopedic and multibracket orthodontic appliances (T2).
Overall, the study sample consisted of 56 subjects (36 treated, 20 untreated) divided into three groups.
The MARA group included 18 subjects (13 male, 5 female) with initial and final ages of 11.70 ± 1.11 years and 15.30 ± 1.20 years, respectively. The subjects were treated for a mean period of 3.60 ± 0.91 years, showing an initial mean ANB angle of 5.66 ± 1.49° and an initial mean overjet of 7.45 ± 1.34mm.  The MARA appliance consists of four steel crowns supported by the permanent first molars (Fig 1). These crowns include loops that connect when the patient occludes. A lingual arch and transpalatal bar were used as anchorage for the maxillary and mandibular molars, respectively. 1 It is possible to accomplish mandibular advancement by inserting steel bands in the loops of the maxillary crowns. There are different sizes of bands (1 to 4 mm in length). In this way, advancement can be performed gradually, while the patient is able of adapt. 1 The group treated with the AcHg combination followed by multibracket fixed appliances consisted of 18 subjects (12 male, 6 female). All patients were in the early permanent dentition.
This group presented initial and final ages of 10.88 ± 0.80 years and 14.06 ± 1.35 years, respectively. The subjects were treated for a mean period of 3.17 ± 1.50 years, showing an initial ANB angle of 5.98 ± 1.64° and an initial overjet of 7.70 ± 2.30 mm.
Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 9 The AcHg combination appliance consisted of a bimaxillary acrylic block, which included an expander screw, a 0.7-mm labial bow, and Adams clasps for retention (Fig. 2). An acrylic cape was

STATISTICAL ANALYSES
Initially, normal distribution was tested with Kolmogorov-Smirnov tests. Thus, all variables showed normal distribution.
The comparability among the three groups regarding sex and initial Class II molar relationship severity was tested with Chisquare tests. Intergroup comparability regarding the initial and final ages, initial cephalometric statuses and the treat-

RESULTS
The random errors were within acceptable limits 14,17 and ranged The MARA group showed a significantly older initial age than the headgear group, and MARA and the control group had a significantly older final age than the headgear group ( Table 2).
The total treatment time for the experimental groups and the follow-up period for the control group were comparable.
Regarding sex and Class II molar relationship severity distributions, the groups presented great comparability.  Table 2: Intergroup comparability regarding initial and final ages, treatment and observation times (ANOVA followed by Tukey tests), sex distribution and severity of the initial anteroposterior relationship of the dental arches (Chi-square tests).
Different letters indicate statistically significant differences.
*Statistically significant at p < 0.05.   Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 17 The AcHg group showed significantly greater restriction of maxillary forward displacement, compared to the other groups (SNA = -1.87°, p < 0.001; Table 4). The control group presented a significantly greater increase in the maxillary effective length than the experimental groups (Co-A = 4.88mm, p < 0.018).  Different letters indicate statistically significant differences.
*Statistically significant at p < 0.05. Table 4: Intergroup comparison of treatment and growth changes standardized to 3.17 years (T2-T1 -ANOVA followed by Tukey tests).
Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study

SAMPLE AND METHODOLOGY
The groups tested in this study represent two distinct treatment protocols. The MARA appliance is usually installed at the permanent dentition, 1 while the AcHg combination can be performed in the early stages of mixed dentition, ideally at the beginning of the growth spurt. 18 Therefore, since the main focus of this study was to investigate and compare the treatment changes between these two protocols, that limitation regarding age comparability might be acceptable.
Notwithstanding, the groups presented approximately a 1-year difference in the initial and final ages ( Table 2). The patients' age could be a confounding factor in this particular comparison, overestimating the effects of one appliance. Therefore, to conduct reliable statistical comparisons, all cephalometric variables were annualized, as previously suggested. 19 Thus, all variables of the MARA and control groups were adjusted to the time interval of the AcHg group (3.17 years). Bias due to confounding factors is common in retrospective studies, and this was an attempt to decrease the chance of introducing bias into the present study.
Moreover, the samples presented great comparability regarding sex and Class II molar relationship severity distribution, which is also essential to obtain reliable results. 20 Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 20 The baseline cephalometric statuses showed statistically significant differences between the groups (Table 3) However, the probability of detecting mild significant differences would be reduced if the correction was performed, and these small differences could be important between these two treatment protocols.
Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study

TREATMENT EFFECTS
The three groups were compared regarding treatment outcomes and growth changes.
The AcHg showed a significantly greater maxillary growth restric- In this study, even though the effect of the appliances seems mild regarding the SNA when the effective maxillary length is evaluated, a considerable restriction of the maxillary growth is noticed in both treated groups when compared to the control (Table 4).
These findings are in accordance with other studies. 1,7,18 The results of this work corroborate with previous studies, with no significant changes in the mandibular component between the groups 13,14 (Table 4). Some skeletal effects on the mandible should have been expected with the MARA appliance, however, Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 22 the functional appliances only induce a temporary acceleration of the mandible development, stimulating bone remodeling in the condyle and glenoid fossa while the appliance is in use. 25 However, when the stimulus is removed, the mandibular development loses intensity gradually, until it reaches the normal values of untreated control. 25 After treatment, the maxillomandibular relationship significantly improved in both treated groups, when compared to the control (Table 4). This improvement is a consequence of the maxillary growth restriction, associated with normal mandibular growth and significant dentoalveolar effects. Most of the researchers who have studied the MARA appliance 1,23,26,27 and the AcHg combination, 14,28 as well as other therapies have also reported similar findings. 7 Nonetheless, it should be highlighted that the AcHg showed superior skeletal effects, compared to the MARA, due to its greater maxillary restrictive effect. Therefore, the AcHg combination followed by fixed appliances was more effective to improve the maxillomandibular relationship than the MARA.
Orthodontic treatment performed with AcHg and MARA followed by multibracket fixed appliances did not alter significantly the predetermined growth pattern. The changes presented in the vertical component are a probable result of normal growth.
The condyle grows in a vertical direction, and the mandible presents a counterclockwise rotation in response to this growth. 29 Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study

23
The maxillary dentoalveolar changes occurred mainly in the incisors ( Table 4). The experimental groups presented significantly greater retrusion of the incisors than the control group.
This finding corroborates with other studies and is a common effect of most functional appliances. 1,13,27 Nonetheless, it is important to highlight that part of these significant changes derived from the multibracket fixed appliances therapy. 22,27 Indeed, to evaluate the true effect of the AcHg combination and MARA appliances, lateral cephalograms after the orthopedic phase should have been evaluated. Thus, this limitation should be considered while interpreting the treatment effects of the appliances tested.
The maxillary molars did not present significant differences in a sagittal perspective, probably due to the use of anchorage control on experimental groups, which is in line with several studies in the literature. 13 The experimental and control groups behaved differently regarding the mandibular incisors' inclination. In the treated groups the incisors tipped labially, while in the control group lingual tipping was observed, therefore, demonstrating significant differences (Table 4). This significant proclination in the experimental groups has been widely reported in functional appliances therapy. 1,14,26 Even though some lingual tipping was expected resulting from possible natural relapse and lingual torque applied during finishing, this tendency remained after treatment. 1 Brito DBA, Bellini-Pereira SA, Fonçatti CF, Henriques JFC, Janson G -Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study 24 Similar anteroposterior effects in the incisors and molars were observed with both appliances after the use of multibrackets (Table 4). Significant improvements in dental relationships were found. Both functional appliances presented a combination of skeletal and dental effects that in association improved the dental relationships. 1,28 All favorable skeletal alterations were not associated with significant improvements in the soft tissue. These findings corroborate with other previous studies. 13,29 CONCLUSIONS » Both treatment protocols, AcHg combination and MARA followed by multibracket fixed appliances, were effective to treat Class II division 1 malocclusion.
» The AcHg presents the advantage of promoting a significantly greater restriction of maxillary forward displacement when compared to the MARA appliance. Therefore, showing greater skeletal effects and more effectiveness in correcting the maxillomandibular relationship in Class II malocclusion patients.
» In relation to the dentoalveolar aspect, both treatment protocols showed similar effects, with a significant improvement of the molar relationships, overjet, and overbite.